// 表示声明一个类型，同时指定类型
var a;
a = 10;
a = 33;
var b = true;
console.log('b :>> ', b);
function sum(a, b) {
    return a + b;
}
console.log('sum(123,456) :>> ', sum(123, 456));
console.log('sum(123,456) :>> ', sum(123, '456'));
function sum2(a, b) {
    return a + b;
}
console.log('sum2(123,456) :>> ', sum2(123, 456));
